Use of time-lapse resistivity tomography to determine freshwater lens morphology

Effects of long-term mixed land use of human settlement and oil palm plantation on the groundwater quality of ex-promontory land

“…It is comprised of fine-to-coarse light-grey sand and gravel, impermeable materials (silt and clay), and fragmented shells. The presence of fragmented shells confirmed that the layers were deposited by a marine environment [4].…”

“…Groundwater has been sampled by using biodegradable plastic bailers from monitoring wells and was preserved in two separate bottles with and without concentrated sulphuric acid to prohibit further chemical reaction in the water. Most of the water samples wereanalysedimmediately according to the standard method [29] by using Ion Chromatography 850 Professional IC (Metrohm, Switzerland) for cations analyses such as nitrate-nitrogen (NO 3 -N) and phosphate ions (PO 4 3-), whilst anions; ammonium-nitrogen (NH 4 -N) and potassium ions (K + ) were analysed by using Ion Chromatography Model ICS-1100 System (Dionex, USA).…”

“…It is recommended to add 0.4 -0.7 kg of P per palm tree per year. On average, most of the phosphate (PO 4 3-) concentration in the groundwater was high which was up to 7.58 mg/L at MW3.It is worth to highlight that there were records of high PO 4 3-concentration on the particular sampling days for examples 123.64 and 46.88 mg/L in MW1 in the same month, 28.89 mg/L (MW6) and 89.84 mg/L (MW13). However, the data were taken out during statistical analysis as they were classified as outlier data which means they were out of data normal distribution.…”

“…The poor chemical condition of the groundwater can lead to the exceedance of the quality standards in receiving surface waters even though they are not influenced by other resources [10]. The high content of PO 4 3-also will intoxicate the aquatic organisms especially the bivalve species. This matter becomes a concern because it could be a loss and harm the local people as the beach in this area is popular among the cockle farmers.…”

“…Construction and exploration of deep wells at Carey Island andKelanang village in the district were also conducted to seek groundwater resources [2].Recently, a further study has been carried out to determine the occurrence of freshwater lens and seawater intrusion in the island [3][4][5]. Other studies on contamination of aquifers and water sources have also been conducted [6][7][8][9].…”